This archive contains maps of radar backscatter from Venus assembled from individual looks collected in observing runs 
            from 1988 to 2020. Those looks are also archived in delay-Doppler format with the PDS, and the documentation for that archive 
            details the data collection steps (https://pds-geosciences.wustl.edu/missions/venus_radar/index.htm). In all but the 2012 
            dataset, the echoes were transmitted from and received at the Arecibo Observatory. In 2012 the Green Bank Telescope was used 
            as a receiver. For each observing year with Venus close to inferior conjunction, there are multi-look views of the "northern" 
            and "southern" hemispheres, defined with respect to the sub-radar point latitude and longitude during the period. All maps are 
            referenced to a 335 E projection longitude. Each map set contains an image in the opposite-sense circular polarization (OCP, 
            sometimes called "polarized") and one in the same-sense circular polarization (SCP, sometimes called "depolarized"). Spatial 
            sampling is at 1 km per pixel, or about 106 pixels per degree on Venus. The individual looks are normalized to the background 
            noise level such that the OCP and SCP mosaics can be ratioed to obtain the circular polarization ratio (CPR). Offsets of order 
            ten pixels with respect to the Magellan-defined cartographic grid may exist across the images and between observing years.